Eccentric Rotor Extruder Research Articles

Low‐cost and high‐performance poly(butylene adipate‐co‐terephthalate)/thermoplastic starch blends prepared by an eccentric rotor extruder: Morphology, rheological behavior, thermal and mechanical properties

AbstractDue to similar processing and mechanical properties, poly(butylene adipate‐co‐terephthalate) (PBAT) is expected to be a fully‐biodegradable alternative to low‐density polyethylene (LDPE) packaging films, thereby alleviating environmental pollution caused by waste packaging films. However, the higher price of PBAT limits its large‐scale practical application in the packaging field. Blending with thermoplastic starch (TPS) to prepare PBAT/TPS blends can reduce the cost. In this work, the PBAT/TPS blends with different compositions were prepared using a novel eccentric rotor extruder dominated by an extensional flow field. With increasing the TPS content, a transition from the sea‐island phase structure to the bicontinuous phase structure occurred near the composition ratio of 50/50. Moreover, the dynamic mechanical analysis results showed that the compatibility between PBAT and TPS first improved and then deteriorated as the TPS content increased. As a result, the elongation at break first decreased slightly from ~1585% for the PBAT/TPS(90/10) blend to ~1263% for the PBAT/TPS(70/30) blend and dropped sharply to ~130% for the PBAT/TPS(40/60) blend. The knowledge obtained from this study will help us further understand the effect of the TPS phase on the micro‐morphology and macro‐properties of the PBAT/TPS blends, which is important for the future preparation of high‐performance PBAT/TPS blends.

Bio-based Polylactic acid/Polyurethane blends with good recyclability and excellent shape stability for solar thermal energy storage

Solid-solid phase change materials (SSPCMs) with low volume change, no leakage, lack of corrosion and extensive service lives are used more and more widely in the application field of thermal energy storage (TES). In this study, eco-friendly polylactic acid (PLA)/polyurethane (PU) phase change composites with good recyclability and excellent form stability for TES were obtained by melt blending in a twin-screw eccentric rotor extruder. The experimental results show that the introduction of PLA is helpful to enhance the mechanical strength and leak-free performance of the PLA/PU composites. When the content of PLA achieved 20% in the PLA/PU composites, the relative enthalpy efficiency (η) of PP-20 is 79.14%, which is beneficial for the function of TES. Especially, PP-40 showed excellent flexibility, reversibility and durability whose tensile stress (14.0 MPa) and tensile strain (48.15%) were pretty good at room temperature. After reprocessed many times, PP-40 showed good recyclability whose enthalpy of fusion reduced (60.69 J/g) but could still reach 91.51% of the original. The above results imply that the PLA/PU composites provide an efficient way for the green use and reprocessing of SSPCMs in the field of TES.

Strengthening-toughening pure poly(lactic acid) with ultra-transparency through increasing mesophase promoted by elongational flow field

Poly(lactic acid) (PLA), as a biodegradable material, finds wide applications in packaging, automotive, and biological industries. However, achieving high strength, toughness, ultra-transparency, and heat resistance simultaneously in pure PLA through continuous one-step manufacturing remains a significant challenge. In this study, we addressed this challenge by utilizing the eccentric rotor extruder (ERE) in combination with cooling rolls to manufacture PLA sheets with outstanding mechanical performance. The ERE's elongational flow field combined with the cooling roller's weak stretching action induced orientation in the PLA molecular chains and promoted the formation of more mesophase, significantly improving mechanical properties. When the extrusion-stretch ratio (λ) value was 3.5, the tensile yield strength, Young's modulus, and elongation at break of ERE-fabricated samples ER-3.5 reached 86.2 MPa, 1777 MPa, and 57.9 %, respectively. Compared to the SE-3.5 samples manufactured with traditional methods, the increases were 38.8 %, 25.8 %, and 9.4 times, respectively. Additionally, the ERE manufactured samples maintained ultra-transparency and high heat resistance, making them suitable for food packaging, biomedicine, and other related fields. This methodology provides an efficient industrial-scale approach for manufacturing neat, biodegradable PLA with outstanding mechanical performance and ultra-transparency.

Constructing synergistically strengthening-toughening 3D network bundle structures by stereocomplex crystals for manufacturing high-performance thermoplastic polyurethane nanofibers reinforced poly(lactic acid) composites

As one of the most promising biodegradable materials, poly(lactic acid) (PLA) is seriously restricted by its notorious inherent brittleness and weak heat distortion resistance. In this work, a novel and simple methodology is proposed using an eccentric rotor extruder (ERE) with a predominantly elongational flow field to manufacture high-performance engineered poly(L-lactic acid)/poly(D-lactic acid)/thermoplastic polyurethane nanofiber composites on an industrial scale. The oriented tough TPU nanofibers (TNFs), rigid integrated PLA hybrid crystals and their good interface compatibility produce a strengthening-toughening bundle structure. When the PDLA content reached 3 wt%, the bundle structures interlinked with each other to form a strengthening-toughening 3D network. This resulted in a high-performance engineered 80L/5D/15T nanofiber composite with super toughness of 74.1 kJ/m2, high strength of 47.3 MPa and superior Young's modulus of 1378 MPa, which are 28.6 times, 85% and 92.7%, respectively, compared with neat PLLA. Compared with those published literatures, the 80L/5D/15T nanofiber composite not only possesses super toughness (more than 28 times) but also maintains good strength (maintain 85%), additionally good heat distortion resistance was also obtained. The performance of 80L/5D/15T nanofiber composite was significantly superior in comparison with biodegradable plastics as well as petroleum-based non-degradable general-purpose plastics and engineering plastics, demonstrating its enormous potential as a substitute structural material in harsh environments. It is believed that the novel and industrial scale methodology opens new perspectives for manufacturing other high-performance engineered biodegradable materials.

A novel PLA/P(3HB-co-4HB)/MWCNT composite featuring enhanced mechanical properties and excellent thermal stability based on elongational rheology

Simple melt blending is the most frequently-used strategy to obtain high-performance PLA composites. However, the thermosensitive PLA displays the defects of poor thermostability, high brittleness and low heat deformation temperature (HDT) in traditional melt-plasticizing equipment based on shear flow field (SFF). In this work, PLA/P(3HB-co-4HB) blends were fabricated via melt blending technology based on the melt plasticization equipment of elongational flow field (EFF) and SFF. Subsequently, Multi-Walled Carbon Nanotube (MWCNT) was introduced into PLA/P(3HB-co-4HB) blends to prepare PLA/P(3HB-co-4HB)/MWCNT high-performance alloy in an eccentric rotor extruder based on EFF. The periodic compression and release of the EFF on the melt promoted P(3HB-co-4HB) in-situ fiberization and formed special microstructure, which greatly enhanced the mechanical properties, HDT, thermal stability and crystallization perfection of PLA. The tensile strength, Young's modulus, elongation at break, impact strength and HDT of the blend containing 20 wt% P(3HB-co-4HB) under EFF were 8.7%, 22.5%, 80.9%, 62.5% and 14.8% higher than those under SFF, respectively. In addition, MWCNT was induced to disperse into P(3HB-co-4HB) phase by EFF, and played a ‘bridge’ role in PLA and P(3HB-co-4HB), thereby obtaining PLA/P(3HB-co-4HB)/MWCNT high-performance alloy with stronger comprehensive performance. The fabricated PLA/P(3HB-co-4HB)/MWCNT alloy provides a reference for preparing biopolymers under EFF and broadens the potential application value of PLA/P(3HB-co-4HB).

Unique Morphology of Polylactide/Poly(ε-Caprolactone) Blends Extruded by Eccentric Rotor Extruder

Unique Morphology of Polylactide/Poly(ε-Caprolactone) Blends Extruded by Eccentric Rotor Extruder

Scalable fabrication of high-enthalpy polyethylene/carbon nanotubes/paraffin wax nanocomposite with flexibility and superhydrophobicity for efficient thermal management

The fabrication and adaptability of a phase change composite severely restricts its further promotion and application in the fields with complex requirements. Herein, a synergistic strategy combining melt mixing, salt template and vacuum impregnation was proposed for the scalable fabrication of polyethylene/carbon nanotubes/paraffin wax (PCP) nanocomposite with high enthalpy and sufficient flexibility. Benefit from the eccentric rotor extruder based on the volumetric elongational rheology, superior thermal conduction paths was constructed by a small number of CNTs (1.5 wt%) due to the decent dispersion of the nanofillers. Meanwhile, excellent thermal stability, high latent heat (150.6 J/g), superhydrophobicity and self-cleaning property of the PCP nanocomposite allow it to serve as a long-term thermal management material in harsh environments. The proposed method can be an excellent candidate for the scalable preparation of PCP nanocomposite for the thermal management of both electronic devices and efficient utilisation of solar energy.

High orientation structure in UHMWPE/BN composites continuously obtained by elongational flow field leading to superior thermal conductivity

AbstractUltra‐high‐molecular‐weight polyethylene/boron nitride (BN) composites have been continuously prepared successfully by eccentric rotor extruder (ERE) based on elongational flow. Optical microscopy (OM), scanning electron microscopy (SEM), x‐ray diffraction (XRD), thermal conductivity test, heat‐dissipation test, and tensile test were performed to investigate the orientation structure, thermal conductivity, mechanical properties, and insulation properties. The orientation factor and thermal conductivity of the composites prepared by ERE were 79.3 and 3.75 W·m−1·K−1, which were much higher than those of composites prepared with a torque mixer (14.7 and 2.73 W·m−1·K−1, respectively). OM and SEM showed that the BN sheets were in contact inside the composites and formed an efficient thermal conductivity network. Besides, the composites prepared by ERE had satisfactory mechanical and insulation properties (>1013 Ω·cm). This study provides experimental and theoretical guidance for industrial preparation of polymer/layered‐filler functional composites.

Continuous mixing process and properties of NR/CB nanocomposites based on elongational rheology

A self-developed biaxial eccentric rotor extruder (BERE) based on elongational rheology was adopted to prepare natural rubber (NR)/carbon black (CB) nanocomposites continuously through one-step process in 1.5 min. The micro morphology, rubber processing analysis, binding rubber content, relaxation time, molecular weight and distribution, vulcanization and mechanical properties of the prepared NR/CB nanocomposites were tested. By comparing with NR/CB nanocomposites prepared by internal mixer, it is proved that BERE continuous mixing process can not only greatly shorten the mixing time, reduce unit energy consumption, but also make the prepared NR/CB nanocomposites have good mixing and dispersion morphology, excellent physical and mechanical properties, high molecular weight retention and binding rubber content.

Toughening and reinforcing waste polypropylene with POE/nano‐SiO2 under elongational flow

AbstractDue to the white pollution, the recycling of waste plastics has attracted more and more attention. In this research, waste polypropylene/Ethylene‐octene elastomer/nano‐SiO2 composites (wPP/POE/SiO2) were melt‐blended using an Eccentric Rotor Extruder (ERE) dominated by elongational flow field and a Torque Rheometer (TR) dominated by shear flow field, respectively. The micromorphology, mechanical, crystallization, thermal and rheological properties of wPP/POE/SiO2 blends were studied. Compared to the blends fabricated by TR, the wPP/POE/SiO2 blends with different compositions fabricated by ERE showed higher tensile strength, flexural strength, and modulus. Particularly, without sacrificing the tensile strength, the notched impact strength of the wPP/POE/SiO2 blends fabricated by ERE increased to 13.53 kJ/m2, a factor of 3 times larger than that of neat wPP. The enhancement of impact strength of the wPP/POE/SiO2 blends fabricated by ERE could be ascribed to the good dispersion of POE under elongational flow and the increase of PP crystallinity. The finding from this work provides an efficient way to recycle wPP.

Effect of elongational rheology on plasticization and properties of thermoplastic starch prepared by biaxial eccentric rotor extruder

Large amounts of plasticizers were added into natural starch for thermoplastic to make it processable due to the high crystallinity and large amount of intermolecular hydrogen bonds of starch. However, the traditional screw extruders based on shear deformation cannot disperse the plasticizer evenly and plasticize the starch well, which affects the comprehensive mechanical properties. In this paper, a self-developed biaxial eccentric rotor extruder (BERE) based on elongational rheology was introduced to prepare thermoplastic starch (TPS) sheets with glycerol as plasticizer at different speeds. The TPS sheets extruded by BERE all have excellent mechanical properties and optical transparency. Scanning electron microscopy, Fourier transformation infrared spectroscopy, X-ray diffraction, dynamic rheometer and universal mechanical tester were used to reveal the morphology, type and strength of hydrogen bonds, crystal structure, dynamic rheological and mechanical properties of TPS to research the effect of elongational rheology on its plasticization and properties. The results showed that the elongational rheology produced during processing process of BERE could obviously promote the dispersion of glycerol in starch and improve the melt-plasticizing effect of TPS, and the comprehensive mechanical properties of the TPS prepared by BERE is excellent with the elongation at break of 226.1%.

Enhancing Chain Mobility of Ultrahigh Molecular Weight Polyethylene by Regulating Residence Time under a Consecutive Elongational Flow for Improved Processability

Improving the processability of ultrahigh molecular weight polyethylene (UHMWPE) and understanding the effect of the polymeric chain mobility has long been a challenging task. Herein, we show that UHMWPE without any processing aids can be processed at a lower temperature of 180 °C compared to conventional processing temperatures (~250 °C) under a continuous elongational flow (CEF) by using an eccentric rotor extruder (ERE). By probing the effect of the residence time of UHMWPE samples under a CEF on the morphology, rheological behavior and molecular orientation, we find that the long polymer chains of UHMWPE are apt to orientate under a consecutive volume elongational deformation, thereby leading to a higher residual stress for the extruded sample. Meanwhile, the residence time of samples can regulate the polymeric chain mobility, giving rise to the simultaneous decrease of the melting defects and residual stress as well as Hermans orientation function with increasing residence time from 0 to 60 s. This also engenders the enhanced diffusion of UHMWPE segments, resulting in a defect-free morphology and higher entanglement with lower crystallinity but without causing obvious thermal oxidative degradation of UHMWPE. This interesting result could originate from the fast chain entanglement and particle welding enabled by a desirably short residence time, which could be explained by the empirical, entropy-driven melting explosion mechanism.

Impact of hybrid nanofillers on the structure and property of polypropylene/polystyrene composites based on elongation flow

AbstractThe composites comprised of polypropylene (PP), polystyrene (PS) and hybrid nanofillers were prepared by a novel eccentric rotor extruder based on elongation flow. The morphology, thermal behavior and rheological properties were investigated. The morphology of the PS dispersed phase changed from circular shape of PP70/PS30 blend to microfiber shape of PP/PS/MWCNTs/MMT composite with an increase of the number of the hybrid nanofillers dimensions. The nano‐TiO2 and MWCNTs were mainly located at the interface, did not change the shape of the PS dispersed phase but reduce the size of the dispersed phase. The hybrid nanofillers containing MWCNTs had better modification effect on the improvement of the crystalline ability of PP compared with the hybrid nanofillers without MWCNTs. The introduction of the hybrid nanofillers did not affect the crystal type of PP, but influence the perfection of crystallization of PP. The hybrid nanofillers had a nice enhancement on the thermal stability of the PP/PS blend. Compared with PP, the low frequency G′ of the hybrid nanofillers filled PP70/PS30 composites increased by two orders of magnitude. With an increase of the dimensionality of the hybrid nanofillers, the restriction of the molecular chains relaxation caused by the hybrid nanofillers was enhanced.

Elongational Flow Field Processed Ultrahigh Molecular Weight Polyethylene/Polypropylene Blends with Distinct Interlayer Phase for Enhanced Tribological Properties.

Herein, we produced a series of ultrahigh molecular weight polyethylene/polypropylene (UHMWPE/PP) blends by elongational-flow-field dominated eccentric rotor extruder (ERE) and shear-flow-field dominated twin screw extruder (TSE) respectively and presented a detailed comparative study on microstructures and tribological properties of UHMWPE/PP by different processing modes. Compared with the shear flow field in TSE, the elongational flow field in ERE facilitates the dispersion of PP in the UHMWPE matrix and promotes the interdiffusion of UHMWPE and PP molecular chains. For the first time, we discovered the presence of the interlayer phase in blends with different processing modes by using Raman mapping inspection. The elongational flow field introduces strong interaction to enable excellent compatibility of UHMWPE and PP and induces more pronounced interlayer phase with respect to the shear flow field, eventually endowing UHMWPE/PP with improved wear resistance. The optimized UHMWPE/PP (85/15) blend processed by ERE displayed higher tensile strength (25.3 MPa), higher elongation at break (341.77%) and lower wear loss of ERE-85/15 (1.5 mg) compared to the blend created by TSE. By systematically investigating the microstructures and mechanical properties of blends, we found that with increased content of PP, the wear mechanism of blends varies from abrasive wear, fatigue wear, to adhesion wear as the dominant mechanism for two processing modes.

Preparation of super-toughened Poly(L-lactide) composites under elongational flow: A strategy for balancing stiffness and ductility

In this work, elongational flow supplied by a novel extrusion device, eccentric rotor extruder (ERE), was employed to prepare high-performance poly(L-lactide) (PLA)/poly(ε-caprolactone) (PCL) composites. Scanning electron microscopy (SEM) evidenced the elongational flow induced in-situ fiberization, in which the dispersed PCL were stretched into nanofibrils, consequently improved the interfacial adhesion of PLA/PCL. Differential scanning calorimetry (DSC), two-dimensional small-angle X-ray scattering (2D-SAXS), two-dimensional wide-angle X-ray diffraction (2D-WAXD) and dynamic mechanical analysis (DMA) were used to investigate the compatibility and crystallization of all composites. Consequently, we confirmed the enhanced compatibility and crystallinity were due to PLA's heterogeneous crystal nucleation on the nano-fibrillated PCL phases and the orientation of the PLA in a particular direction, which were considered induced by the elongational flow. Ultimately, we showed that the elongation at break of PLA with a low loading (20 wt%) of PCL is significantly improved to 476.7%, which is over 57 times that of the neat PLA. Meanwhile, the slight reduction in tensile strength is less than 20%. Enhanced thermal stability was also monitored due to the improved compatibility of PLA-PCL and the increased crystallinity of PLA.

Toughening and reinforcing wood flour/polypropylene composites with high molecular weight polyethylene under elongation flow

Toughening modification often reduces the stiffness of wood–plastic composites (WPCs). In this study, wood flour/PP composites with high molecular weight polyethylene (HMWPE) were toughened and strengthened under elongation flow by using an Eccentric Rotor Extruder (ERE). Under elongation flow, the incorporation of HMWPE into wood flour/PP composites improved the tensile strength, flexural strength, flexural modulus, notched impact strength, and un-notched impact strength by 23.2%, 24.9%, 26.3%, 67.3%, and 67.7%, respectively, compared with wood flour/PP/HMWPE composites processed by using a torque rheometer. The strengthening and toughening mechanisms of the resulting composites were investigated. The former is related to the oriented crystals and wood flour, the higher polymer crystallinity and the improved interfacial adhesion between the polymer matrix and wood flour. The latter depends on the better HMWPE dispersion, the strengthened interface between PP and HMWPE and the better interfacial adhesion between wood flour and the matrix. These results provide exciting opportunities for further widespread functional applications.

Morphology, thermal behavior, rheological, and mechanical properties of polypropylene/polystyrene blends based on elongation flow

Binary blends comprised of polypropylene (PP) and polystyrene (PS) were prepared by a novel eccentric rotor extruder based on elongation flow. The morphology, thermal behavior, rheological and mechanical properties were investigated. As the enhanced mixed dispersion based on the novel extruder, the dispersed PS phase were uniformly dispersed in the PP matrix when the PS not more than 40%, and a distinct cocontinuous phase structure emerged when the PS content was 50%. The size of the dispersed PS phase related to the PS content and the processing flow filed influenced the crystallization behavior and the thermal stability of the blends. The PS droplet with small size could act as a nucleating agent for PP to improve the crystallinity, and PS droplet with large size could promote the thermal and heat transfer between the PS droplets and PP matrix which decreased the thermal stability. The rheological results showed that the compounding with PS into the PP matrix increased the storage and loss modulus as well as the complex viscosity of the materials. When the PS content not more than 20%, the blends showed good impact resistance, and PP/PS blends 30% PS showed good tensile and flexural properties. This study gives a new perspective for the structure and properties of the binary PP/PS blends prepared based on elongation flow.

Improved Properties of Metallocene Polyethylene/Poly(ethylene terephthalate) Blends Processed by an Innovative Eccentric Rotor Extruder.

In this investigation, metallocene polyethylene (m-PE) was melt blended with poly(ethylene terephthalate) (PET) with an effort to achieve improved mechanical properties using a novel eccentric rotor extruder (ERE) without the addition of any compatibilizers. The phase morphology, rheological properties, crystallization behavior, and mechanical properties of the fabricated blends were carefully studied to explore the effect of the elongational flow field on the dispersion and mixing of PET in the m-PE matrix and the interface of the two immiscible polymers. For comparison, a conventional twin-screw extruder (TSE) was used to prepare the same blends as references using the same processing condition. It shows that the elongational flow field in ERE is much more effective to disperse the immiscible PET in the m-PE matrix with a smaller particle size and a narrower particle size distribution, compared to the shear flow field in TSE. A compatibilizer, ethylene-co-methyl acrylate-co-glycidyl methacrylate (E-MA-GMA), was added to the m-PE/PET blends during the processing using TSE and ERE. It was observed that the improvement of the tensile property by adding the compatibilizer is marginal for the m-PE/PET blends processed using ERE, which indirectly proves the high effectiveness of the elongational flow field on the enhancement of the dispersion and mixing of PET in the m-PE matrix and the interface interaction.

Multizone barrel temperature control of the eccentric rotor extrusion process

Abstract The eccentric rotor extruder is a new kind of extrusion equipment with novel structure and outstanding engineering performance. As the structure of the eccentric rotor extruder is different from that of the traditional screw extruder, the control of the barrel temperature becomes important, including avoiding the influence of heating coupling and achieving high control accuracy. A neuron proportional-integral-derivative (neuron-PID) control algorithm of barrel temperature for the eccentric rotor extruder is introduced. The neural self-learning algorithm is able to tune PID parameters online, and the particle swarm optimization (PSO) algorithm is adopted to optimize the initial weight coefficients of the neuron. The experimental results show that the PSO-neuron-PID controller has the advantages of low overshoot and high control accuracy, and the influence of heat coupling can be counteracted effectively.

Numerical Simulation of Mixing Characteristics in the Eccentric Rotor Extruder with Different Process Conditions and Structural Parameters

Numerical simulation was performed with the computational fluid dynamics analysis software POLYFLOW to investigate the influence of different process conditions and structural parameters on mixing characteristics of the eccentric rotor extruder. The intensity of shear and elongational flow strengthened when the rotational speed increased, but the time for material to stay in the extruder will be reduced. At the same time, the increase of radius and eccentricity could effectively promote the mixing performance. On the contrary, the mixing capacity reduced with the increase of the pitch. The results can be useful to optimize the structure design and guide production.